Stickies in Recovered Paper Fiber Suspensions: A Tutorial Review

Abstract

The paper industry has achieved relatively high levels of recovery and reuse of cellulosic fibers by the recycling of paper. The industry’s record of recovering material from used paper products far exceeds that of, for instance, the plastics industry. However, in the course of that success there are challenges. This paper provides a tutorial review of problems related to the stickies content of recovered used paper material. The review considers what stickies are composed of, how they can affect papermaking and its products, and how papermakers can minimize their adverse effects. Stickies tend to be problematic in mills without deinking systems. Though some stickies can be removed by screening, much of the material is expected to deform and thereby pass through industrial screens. Larger stickies (macrostickies) can be removed using hydrocyclones, whereas smaller ones (microstickies) are often removed using flotation. Other approaches to dealing with stickies include using detackifiers, which essentially means covering the stickies with a polymer or a mineral product. Production teams can optimize conditions to retain the stickies, ideally as small particles, onto cellulosic fibers. Because the processes are complex, and the composition of recovered stock tends to change over time, continuing efforts will be required. Effective control of stickies can be expected to require effective collaboration among people at the mill, chemical supplier companies, and machinery specialists.